Recovery of tar acids and other products



Oct. 6, 1931 S. P. MILLER RECOVERY OF TAH ACIDS AND OTHER PRODUCTS Filed July 16, 1927 2 Sheets-Sheet 1 WM, Rm,

WPI/MM INVENTOR PMM/awww ATTORNEYS Oct. 6, 1931. s. P. MILLER RECOVERY OF TAR ACIDS AND OTHER PRODUCTS 2 Sheets-Sheet 2 Filed July 16 1.927

l INVENTOR gam( P mi@ Paw/f1 f cil) YPatented(Y Oct. 6,` 1931 j entrancevEARMEEEE'` MILLER, or veinenv RIDGE-@NEW JERSEY, kiissIeNor; 'ro THE f f BARRETT coMPANmoE NEW YORK, NrY., A CORPORATION or NEW JERSEY .TENT ortica REcovERYoE TAR ACIDSIYAND OTHER IRonoc'rs -AiApplication led July 16,

This invention relates tothe producion of i tar acids-'and otherV products vfrom vcoal lar L5 is yonlinarily subjected to distillation inr tary stills forythe production.v therefrom of dis-r tillate `oils and vpitch residues; The lighter of carbolic oil fractionA produced by such disvvtiliat-ion is then subjected to treatment. to extract the phenols orv tar acids therefrom. It is necessary to subject the tar to distillationbefore the tar acids can bei extracted, be-

cause kt-he Vpresence oftarry constituents in lthe tar itself vand in* the tarry oilsvdirectly produced from the coke oven gasesr interfere `With .and prevent the Yextraction of tar acids from the tar or tarry oil, v l .j The coal tar produced from the colte oven gases at' the coke -oven k.plant is commonly transported to `tar distillation plants, more or lessremotelysituated, and there subjected tofdist'illation in externally heated tar stills. This shipment or transportation .of rthe tar requires handling and rehandling ofthe tar 5.,- with incidental losses, as VWell as ad'dedfexpense of transportation, and the distillation of they tar Vresults indecompositionof more Y orless of the oilconstituentsof the tar with reduction infyielrd ofgvdistillateoils and increaseV in lamountfof pitclrresidue, andin the carbony content of 'suchiresidue The present invention keliminatescessityY of transportationof tar to a tar dis- Vl `rtillation plant, and eliminates"orpminimiaes: the lossesofrtar in ,handling and transportation and fthe. decompositionof the oil constituents'of the tar on distillation. It provides improved"methodivhereby tar acids can bevdirectly recoveredat'the colte oven-plant from tar and tarryoils, and also from coke fiile i lief i 192i'. "serial No. 206,368.

' ing enrichment of the gases in tar acid* Oils and y'With'the production Vof a pitch residue ofloW' carbon content. The enriched gases resulting from such distillation are then subjected lto a cleaning treatmentto separate pitch vparticles 'therefrom at a suiiciently high temperature toleave tar acid oils inthe formof vapor, and the resulting cleaned gases,- freed from heavy tar and pitch constituents, are then ycooled to condensetherefrom loils richA in tar acids which are extracted for the recovery oftar acids therefrom. Naphthalene', as Well astar, acids, can advantageously be recovered directly in a state of high 'I6v purity from such oils. y

f When ordinary coke oven gasesare cleaned with an electrical precipitator at a vtemperature sufficientlyY high to permit the gases to Vbe passed through an ammonia saturator above the dew point ofwvater, a large part of thevapo'rs of carbolic oils will remain in the vapor state and can be condensed from the gases after the gases havepassed through the saturator, and thetar acids extracted from theresulting oils, as described in my companion 'applications Serial Nesi 206,370 and 206,365. If the gasesare cleaned at a higher 'y temperature and cooled to separate oil therefrom ata temperature above the dew point` of Water and before passing the gases through the saturator at suchk temperature, the oil Will; be arelatively heavy oil, containing relatively small amounts of tar acids, mainly higher boiling tar acids, such oils being suitable for use directly as creosote oils, as described in my companion application Serial No. 206,365. In order to separate oils rich in tar acids from ordinary coke oven gases, the gases'must be cooledto alower tempermain common to anumber of/ovens.

asr

i Vrature,V for example, around o to 35o C; and

if such` cooling precedesthe passage of the gases through the ammonia saturatonavater "'Will'be condensedV from the-gases along vvith 5 the tar acid oils, and this Watervvill contain l' ammonia,v Which must be recovered therer' from, ,e.A g., by distillation. f Processes 'by which tar acid oils are directly recovered n 'from coke; oven` gasesV prior to passing-'the `gases through-the vsaturator at-alovv temper` Vature,qare described in myA application Serial` Nos. 202,736, 206,366l and 206,367.

The process of thepresentiinventioniis"an if improvement upon the processes 'of my said lation of tarV or tarrycils to distill tar acid oils therefrom bydirect contact with hotfcoal Y .distillationases suclrasf coke oven frases,

' moival; Yof heavygtai"` and pitc'h constituents iV ,therefroivnl;v andthefzenriched gases are then subjecftedto c oolingfor the separation of. tar yacid oils,o`r of both creosote '-oils'and'tar acid oils, vbefore theg'ases are'passed tothe am- Y monia saturatorl .l e -I l @Ordinary coleoven Y dividual. jcoke ovens at afhigh1 temperature, around, 6000 toOOoiC., ,or'higheig and are commonly-passed,through uptake ,pipes lead- ','ingfrom the individual. ovens to v a collecTtplr e heat which the coke oven gases contain is cominonly dissipatedyby thel introduction of a larg'eamount of ammonia liquor, or of amlmonialiquor and tar, into'the gases injtheool-V lector mainA and inY the pipes leading Jthereto,

and by external cooling-ofthe pipes through ivhich the gases pass,andby subsequent coolying in the condenser.` ,lhelieat containedin v i thefhot coke oven gases vfromwa single-oven isl r many'times'thatrequired to distill the amount of ltar.V producedsfrom the gases Y yfrom `such x s oven, While'the'gasesfroni abatteryofovens,

` forfroni-agroup of ovensunited toa single collector main, farei capable g, of Ldistilling 'an amount oftar ina-nytimes that ordinarily produced from thefbattery, if thetar is brought into* intimate Contact with the gases, so that the heat-.of theg'ases is efectively utilized- :v n :Il-"iccordi-ngsto,A thet'fpresent invention, the gasesfrom asuthcient number of ovens lare em- :ploved yfor distilling tar or tarry` oils? by inlV i i' -ltr-oducing the tar or tarryoils directly into A y, ntim'ate contact: with :the .gases vvhilefStill high teni-perature,l thereby distilling thegtar therefromffSuch" distillation offtar or tar f acid oils Ybybringing them into intimate contact -Vvvith the hotfgases results' in greatly 'enfriching the gases injoilvapors, and;particu'- `:lai-lyA in tar acid `oilj vapors'.v 'orfv example,

the content of oil vapors ordinarily carried by f -c'olrel oven Y gases iso'nlyV aroundgon'e 'p er y cent,

companion applicationsfand involvesy distile gases leave the in e creasedto around ten per cent, or in some cases Y as highv as y fifteen Vor twenty. per cent. This radical increase in vaporcontentof the gases malresnecessary'the cleaning'of the enriched gases'at a vmuch higher'temperature lin order :to maintain ythe?V tar faci'd'oilsinvapor form. Y and to recover a high yield thereof, and make possible also the'r'ecov'ery of a large amount of tar acid oilsata temperature suiiiciently highvv thattlie gases canl thereafter be passed through the ammonia saturator at atemperaf invention, the enriched gasesre'sulting from the distillationofthetar or tarry oil therein, .are subJected'to'a cleaningltreatment atta high temperature, suliicient to --maintain the Y arate an oil rich in tarac-ids, from Which'the tar acids can be directly vand advantageously extracted;` Where the maximum yield of tar acid oils is t'obefcollected inasingle condenser, the gases canbe cooled to,k a lovv' temperature, Y'around 25 .,to v35C C., 4before* passing them tothe ammonia' absorber-por saturator;

butla large proportionfof the tar acid oilscan be recovered at a temperature` above the devv point of dater, and theg'ases can then be passed tothe ammonia absorber or 'saturator above thel fdeW point of Water, With subsequent furthercooling ofthe gases to separate additionalv amounts of light tar acid oils therefrom, prior tothe final scrubbing ofthe gases to recover coke oven light oils e. g., ben- Zol, toluol, etc. therefrom. i 5

lThetar or ltarrvV oil Vto be distilled, 'according tothe presentlfpr'oc'ess, may be ordinary coall tar,comprisingv the total tar constituent recovered from cokev oven gases', or Vmay be VaheavyA Vtar A'such is separated` vin the collector 'Inain of an ordinaryy cokeoven plant,

or it be the vtari-y.oilseparated from the gases 4in 'r the(coolersg or c'ondensers of the orjdinary colse oven Vby.product system.V Where the fonlyftar, Yavailable;tobe distilled is that greater part ofVV the" ,batteryl can 'bei condensed rvandu Coledin the ordinary 'manner' for Vthe .f separation ofheavytar` and tarryfoils therefrom, and the gases'fromla-fetv'only ofthe ovens Vemployed for the distillation of the', Ytar;E llllfher'e taris produced by a large num [ber of batteries, the lgases, from'arsinglebat- 'i 'ture'above the devvj'point ofvvater. Accordv ingly, in the improved process ofthe present' .i Y tery -m'aybe employed {or'thei dis'tillation, lor A part-,fof theVv gasesof the :battery,f.y tor vexam-v ple,the gases collectedfin asingle collector main. :fj Tar 'from' an outside source-such as y anotherfcoke oven1 plant,.orfrom gas retorts ftliorizontal, vertical oriinclined') or low tem- ;j v perature-carbonization tar, riclrin taracids, Y. cany besubjected to distillation, accordingk to the present invention, andi-the resulting en.- riched gases -treated forthe direct recovery ottar acidloils therefrom." Instead of using the total tarifromv the battery, only the lighter tar orftarry oils, such as are commonly thrown down inthe coolers or` condensers of a; byproduct system, can be employed. These tarryoils are rich 'intar acids naphthan lene,fan'd, by'distillingthem in thek hot coal 'distillation gases,*a very great enrichment ot vdirectcontact With the hotcoke oven gases canbe carriedjout,forexample, as described in my prior applications, Serial Nos. 166,081,

172,962, 179,209,'15 8,137, 181,366, 197,029,0r 171,9551 yFor example, the tar or tarry oil can t beisprayed' or otherwise. introduced inteinyeo timate contact With the hot coke oven gases Vin an ordinary-collector main, or in a short collector main, orinfotherform ofstill in which the tar or vtarry oil is brought into intimate contact withthe hot cokebven gases.

The distillation ofthetar or tarry yoil re- I lsu'lts in the production'ota pitchresidue and,

v:depending uponithe extent to which the disc tillationfis carried,I ahardflor'high melting point pitch can `be produced, or a softer and VloWergmelting .point pitch. So also, theextent tovvhich the distillation is carried will determine vthe character of the vapors Which l .are'distilled from.the't'ar or tai-ry oil, and

vvhichenrich the gases employed `for the distillation. 1 Where A'the' distillation -is carried up'toan extent such thatahigh melting pitch l is. produced, considerable enrichment of `the v gasesin heavieroil constituents vvilltake place. -By `'limiting the distillation, however, a-much `greater enrichmentof the gasesfin lighter oil vapors can beobtairied, particular'-` f ly in oil vapors rich in tar acids or naphthalene, but particularly so when the tarry oils, yrich in tar acids and naphthalene, such as are condensed in'theordinary condensers of a Y by-prod uct recovery system, are subjected to regulated distillation. y f

- 'Dependingupo'n'the temperaturelat Which gthe cleaning ofthel enriched gases takes place,

i Ythere =may`be condensed from the cleaned Vgases only atar acid oil,"or there may be condensedboth aV creosoteoilat-a higher temper- Vj aturefanda tar acidoil. at a lower temperaturei'v4 ljWh'ere only a tar acidoil is'to be di-Y Y' VQrectl .recovered )theenriched rvases can be Y. a v a:

lira

treated, at a temperature 4such that alow melting point pitch, for example, vhaving a .are to be successively condensed fromthe .melting pointV around F., is separated therefrom, suitable for use directly for road f construction purposes, while leaving a large amount ofv tar acid oils-in vapor form. The temperature at which the cleaning of ythe gases andthe separation-of the pitch partil clestheretrom is effected, Will vary with the extent of the enrichment,but will be consid- 'erablyhigherthan the temperature'at Which ordinary coke'oven gaseswill yield a pitch 7 ,5 of vsimilar melting point. Vhereas, for example, With ordinary coke oven gases, Where a temperature of only around to 120 C.

Willigive a pitch vot, meltingV point around 105-to^110 F.,-With enriched gases, greatly enriched in'tar acid oil vapors, a much higher temperature, around to 150 C. or higher may be required. `By subjectingthe gases.at'suclrtemperature to the action of an electrical precipitator,a valuable low vmelting 1 point pitch can be directly produced and tar4 .acid oils'can be subsequently condensed from the cleaned Vgases and extracted for'the rccovery of'tar acids therefrom. Y

-vWhere both 'creosote oils and tar acid yoils it? 'cleaned enrichedor unenriched gases, a much higher temperature is required tor the clean ing operation. For example, a pitch of meltl ing point around 300 F. can be separated from thel gases when the cleaning. operation is carried out ata' vtemperature around e. g. 320]G. depending upon the extent of the en- 'richmentof the gases. They distillation of tar with the hot coke oven gases can be-car- 90 riedto an extent .which will give even a higher 'melting V'point pitch, for example, having a melting point around 40001?, or higher, with passage of kthe resulting enriched gases through the relectrical .precipitator at the ,195 vsame temperature, or at a regulated lower temperature, which will give a lower'melting point pitch romthe precipitator, While leaving in the gases a large amount of oil vapors. The enriched gases can then be condensed llo first, to" separate creosote'oils therefrom; tor

example,at a temperatureof about C., and subsequently further condensed to separate carbolic orf-tar acid oils therefrom, either by cooling to a temperature around 25 to 35 C., inthe lcarbolic oil condensersor bylimit- :ing the cooling softhatfthe gases leave the cooler or condenser While still at a temperature "abovethe' dew point of Water, such thatv they' can be passed to the ammonia satura-tor 12,0 atx a .temperature above the dew point of Water. When the tary acid oil-v is condensed f 'f'rom the enriched gases;y .at a temperature above the-dew point of Water, the present in- Y vention provides an advantageous method of 125 recovering ammonia directly from-the enriched gasesbyfpassing them through an ammonia absorber or saturator'at a tempera- `-ture;abovethe dew point of Water, such that the'l ammoniavis recovered from the, gases 1,30

`Withoutdilutionfby! condensedswater.. g SSuch y vdirect recovery :of ,y ammonia from the gases rabove .theV1 dew point. of Waterv will still leave some ,of the lightercarbolic'oil's inthe vapor j forni, 'and these-oilsl canY be subsequently condensedandre'covered by subjecting .the gases leaving theseparator. first to-[cooling toga temperaturearound to ,309 `Catofseparate y "additional carbolic oil, and then passingthe gases to the scrubber orv absorbergtorthe coke oyen-light oils.; .'Inlsuchfcase, therecovery ot 'tari acid oilswill beV atWo-stage recovery process, the greater partiof the tar acidoilsbeing Vcondensedand *recoveredbefore' the-gases 'l c l passl through the,` ammonia saturator, and a urthe'riamountot rlight carbolic'oils being recovered; kafter vthe lgases pass through the ammonia/saturator.. g Y, ,1 f Where the advantages incidenttothe d1- l rect recoveryl fo.fammonia r above the `dewl "pointiofwater,are not.' to be obtained-,the

l" entire carbolicfortar acid oil. can. be recovf ered inz artsingle.,.,operation..:by: .Cooling the gases kat once tora Y temperature around :25 tra/359C., and separating the condensed tar Aacid Ioil therefrom, andthenlpassing the' -g'aseszeitherfvvith or .Without reheating, to

the ammonia acidabso'rber, VVor `Withdut Vre-v heating to'theordinary Waterabsorber, andfinal-ly, o the; `scrubber or` absorber for. the

' l' Thenoperation ofthe Vpresentprocess can advantageously be.'carriedfout- With circulationof hot tar 0'1" pitch' through the(V collector .advantageously IbeY femployedf fand'. Y distilled main' or vthrough a smallI collector main, and f With spraying oftar or pit'chintoj the vcol;

lector main jwithresulting distillation of the tar or pitch and enrichment of thel coke oven gases in vapor content resulting romthe distillation. l Instead otusingtar or pitch, the light. tar or-tarry oil from'v the condensers of theordinary Vbyproduct recovery system can sutliciently.- to remove therefrom; l.tl1e,g1eate`r 'p'art'lor `allot thet'ar acid oils together with l vnaphthalene,leaving apitchi` .residue-*ot i -hi'gheror'lower1Ineltingpoint.' l-By`,operat-V z ingfin'this.Way,:"apitchproductfcangbe di-l jrectlyj,produced' in the collector. main# and anotherl ypitch 'product Ycan lbeVV separat'edfinV the electrical. precipitat'or,F Which maybe y i' keptjseparate,or which may be reluxed back n yand :admi-xed with the pitchproductvfrom the collector'xn'ain. ."llhereafter'V the enriched gases, cleaned,l inv-the electrical precipitation 'i and #still -containingfa large amount Y offtar -ac'id' oil vapors', arelsubjected to 'coolingfiand condensationfforthe separationfot a tar acid i oil th'erefrom`, Which is' extracted l:torthe refvapors, a greatly increased yield 4of clean -xting free of thetary acidsifr'om `vthe' small tar acid. extracting appar f Y' tszesal I quentlyfcondensedas creosote `oil prior to f vthecondensation Lof the taracid oil frOIIjthe 'vapors at av lower temperature. f -f-Becaus''eot the very great enrichment of the gases in oil oils can ybe directly obtained, andthe carbolfic oilscanfbeA obtained-,in large partV atfa,Y temperature above the dewfpoint ofwater', so

that the gases i afterl theA` separation'fof such carbolic oil cangthen be passed 1 directly to thesaturatorata temperature-above the dew ApointoiWater, Where'this is desired, i

,. The extraction ofthetar acidsforphenols fronithe carbolic or tara'cid oils recovered inthe present process before thefgases pass through the ammonia saturator, may be,tor

example, with a solution of'y caustic alkali, suchas tenV percent 4caustic 'sodafsolutiem which will combine'with the ,tari acidsto forni the sodium saltsthereof, and-"by "separa-y tion Vot the resulting' carbolate solution- `from they extracted oi'l. kThe carbolatef solution. 1 can then be treated to decomposethesodium v salts and fset* freey the plienols f ortar acids, v

y'for example, v'by treatment -With'c'aibondioxide to setffree mostof thetaracida-andl by 'adding a small-amountof sulphuric: acid to the separated tar acids tocomplete` the'lset` amount :of .,carbolate solutionstill remaining dissolved in the,separated taracids. The

tar* acidsjsoA extracted' and #separated vmay then be further. refined vbydistillation, iffdesired, to separate .themfnto :relinedf commercial'fproducts.V The'yextracted'l `o il,; from Which the Vtar acids have-been'extracted, can be employed forsolventspurposesor'as a `'lamp black oil, or -it2canvbe blended With "'pitclrto `form a uel'producnsuchas de scribed in my companion application Serial No. 206,369 which has .maturedinto-Patent A The invention iyillbeifurther described in connection lWith thejapparatus illustrated, in

'a' more korf-lessconventionalf: andadia 'rammaticrniannerf'in'the accompanying. crawings Which show Qa. cokel ovenp-lant' byfprod otthe .process oftheinventioir f j p Y In theaccompanylng draWings,-' f

.uctj recovery systemadaptediior the'practice "Fig` l is a plan View of a portion of a coke rovenv plant-and Vluy-product recovery system adapted for the practice Aof the"inventionf;Y

' Figq isi an enlarged., section Tof theelectricalv 'precipitatorv and collector main it Y Fig. 31s an"en larged-viewAY of-on'er for-mot :Fig: eis a sectional Vele'vation of the; eleci tricalprecipitator; and fl' p sFigyl-shows-one formotcondenser'.

Y 'Tlf-he apparaus illu'stratedinthe drawings Y "compriseszp'art ofV a coke `oven battery, 5, the

Vindividuallovens o'vtwhichiliave individual p f collector main- 7," having a-'centerjbox .8, and

y'which'collector mainj may be' the' ordinary collector [main common *y to A a considerable number of ovens, ora short collector main ycommon to only afew ovens, depending'upon the amount of tar ortarry oils to be distilled therein. f'

- intimate contact with thehot gasesentering Tar or tarry oil isr` supplied to the collector main and {goose-necks, through sprayy noz'- zles 9 and 9 therein, from the pipe 10, connected t a suitablesource of tar or tarryoil. The introduction of the tar or tarry oil into and passing through the collector mains will result'in distillation of thetarl or ta'rryoil .and the production of apitch residue of higher or loweraneltingpoint, and the enrich-` ment ofthe gases" in the oil vapors produced bythe distillation.y The pitch residue will lescape from the collector main through they center box 8and'thefoutlet pipe 11, to the receptacle 12, androrms one of the products of the process which canlbe kept separate, or which Acan be admixed with'the pitchfrom thezelectrical precipitator. A fk y The enriched gases'lleaving the collector rnainare conducted through a pipe 14, to an electrical. precipitator 15, preferably closely l, ad'j'acentto the collector'main in orderthat the temperature Aot ythe gases may notbe re# duced to any considerable extent between the c 'ollecfor' main thehprecipitatonv AThe precipitator may bero'ffany suitable orm of y construction. As shown it consistsolf a shell enclosingfaY number of tubes 15 supported in hea'ds/16'and 17 within the shell. An in1et18 l near the bottom'communicates with va chamber19, which `is v'partially separated from the tube vsection by a btdlieg` An 'outlet 21,.per4

mits the escape otthefcleaned gases l:trom the separator. A plurality of electrodes, 22, lin the form of'metalrods, extends through the tubesv l5 and 'is supported from. a bus bar 23, located'nearthe upper ends of thetubes.

Thebus bar extends at both ends intocasings 24, whichencloseinsulators 25, upon which the bus bar isfsupported. The hightension, currentline extends intoone of the casings`211k and*connects the bus' bar 23,1 thus supplying the'V necessary current from any suitable source ofv uni-'directional lcurrentfoii vlngh tension. The casing of the'separator'is f `grounded or otherwise connected to the source of currenty tocomplete the'circuit.

The casing and :tubes form the positiveelec- 'f trode the electrodes connected to the bus bar beingv negative. The form and varrangement vof thebus bars in the circuit canbe varied.

The arrangement should be such astosupply high ,ten sion ,uni-directional current s to the electrodes,thereby permittingk a continuous .discharge between the electrodes and-the tubes'throughwhich the 'gases pass.

-f Thezgases from the collector mainenterthe electrical precipitator carrying inl suspensiony ,'pa'rticles of pitch which are separated inthe'Y electrical precipitator with the result that the pitch'product collects in the bottom of the separator and 'runs out through the pipe 25 to .ai pitch receptacle-while the-gases freed from pitch particles, and still containing tar acid yoil vapors, escape through the cross-over main 26 to the condensing system. The condensing systemv shown includesonly a single condenser 27,V of a construction illustrated in -F 5, and provides forfthe recovery of a tar acid oil fraction Without'provision for also recovering a higher creosote oil fraction. The condenser shown is an indirect conden- .ser comprising tubes 28 jthrough which the gases pass in heat exchange relation with a cooling liquid such as water,vwhich is circulated through a casing 29, surrounding'the tubes. rl`he gases enter the condenser throughy the cross-over main 26, and -escape therefrom through the gas outlet pipe 32.

YThe tar'acid oil condensedfin the condenser is withdrawn through the outlet pipe 30, to the receptacle 31. s c' From ythe condensers the gases pass through theexhauster 33,- and then through the ammonia saturator 34, and thence to the scrubber or absorber for coke oven light oils V(not shown). Where they maximum yield of tar acid oils is to be recovered inthe c'onden-A ser 27, the' temperature of the gases may be lowered to 25 to 35 C., and thereafter `of light carbolic oil before they pass to thev final scrubber for the coke oven light oils.

The tar acid oil condensed in the condenser 27, and collected in the receptacle 31, can be freed from any accompanying ammonia liquer, incase the condensation is carried out at a sufficiently low temperature to condense 'ammonia' liquor with the oil, and the ammonia liquor can be collected in the receptacle 41 and the oil in the receptacle 35. vThis oil is then subjected to extraction in the extraction apparatus 36, which is shown yas comprising a tank having suitable agitating means, 3 7 therein. The extracting agent, for example, a ten percent solution of caustic soda, `can be added in .suitable proportion to the tank through 'anfinlet 38, and mingled with the oil by agitation Auntil ,the extraction is completed. rThe neutralor extracted oil canl then be returned through a pipe 39, and the carbolate solution comprising the conrbinedtar acids and alkali solution, can be creosote oils, Whiclrcomprises subjecting tarv y to distill the tar and produce a pitch residueand enriched gases containing creosote and tar acid oil vapors, subyecting the resulting VV3. The method of producing tar acids and to intimate contact with yhot coke oven gases enriched gases to cleaning with an electrical precipitator ata suiciently7 high temperature to leave creosote `oil `and tar acid oil vvapors therein,v cooling the resultingcleaned l i gases so as to separate a creosote oil therefrom and subsequently further cooling the gases to Y separate a tar acid oil therefrom before passf ing the gases through an ammonia saturator'g and extracting tar acids from the tar acid oil.

Y y fQThe methodof treating coke oven gases,

which compirises enriching `hot coke ovengases ata high temperature by distillation of Ytar "or, Aoil' therewith,V passing the. enriched L gases While still at a suiiiciently highjtem- Y peratureto maintain creosote oils in the form ofl vapor through an electrical precipitator ite-separate pitch fromthe gases, and cooling 'the resultingjgases to aftemperature sufficient toremove creosote oil therefrom before passfing the gases through an ammonia absorber,

, las,

Y p the temperature to which the gases are cooled f vto remove creosote oil therefrom being such that the gases are left at a temperature above the dew 'point ofthe gases forwater.

5. The method of treating coke oven gases.

which comprises distilling tar or tarry'oils by intimate contact Withhot coke oven gases after the gasesileave the coke ovens and before-they have been cooledvto a low temperature; subjecting the resulting enriched gases,

containing vapors from the distillation, to Vthe action of an electrical precipitator at a suiiiciently high temperature to separate pitch therefrom and leave ytar acid oils in the form of vapors, Land-cooling the resultin gases into separate tar acid oils therefrom Vbefore passing the gases thru an ammonia absorber. the temperature to Which the gases arel cooled to remove said tar acid oils being above the dewpoint of the gases for Water..

6. `The imlvirovement in the process of claim f 5 in which the gases, after leaving the saturator at a temperature above the dew point of Water. are further cooled to separate a further amount of light tar acid oil therefrom and subsequently'subjected to vscrubbing for lthe recovery of coke' oven light oils.

f In testimony vvhereofI` aiiiX my signature.

STUART PARMELEE MILLER. 

